Immunologic techniques were applied to the study of Epstein-Barr virus (EBV) oncogenesis in nonhuman primates. Tumors and fatal lymphoproliverative disorders were produced in a white-lipped marmoset, common marmoset and owl monkey. Specific cell-mediated immunity, immunosuppression, and serum blocking factor were associated with tumor appearance in the white lipped marmoset. A rabbit animal model was developed for Herpesvirus saimiri oncogenesis. Several anti-inflammatory agents and retinoic acid inhibited the production of EBV nuclear antigen, EBV antigens induced by 12-0-tetradecanoyl-phonol-13-acetate (TPA), DNA synthesis and transformation.